1. Field of the Invention
The invention is related to an assembled structure of a plurality of laminated plates, in particular, a structure wherein the outer surface is enlarged for promotion of heat radiation therefrom.
2. Description of the Prior Art
In electronic parts having any current circuits other than superconducting circuits, an electric current flowing therein inevitably generates heat.
The heat is radiated into an atmosphere surrounding the electronic parts.
If the quantity of heat generated in the electric circuits exceeds what is removed therefrom, the electric parts accumulate heat therein and naturally increase their own temperature.
An excessive temperature increase of the electronic parts finally brings the device to thermal destruction.
As a measure of avoiding such a problem, it is conventional to enlarge dimensions of the electric parts to thereby sufficiently increase the outer surface and its heat capacity. This realizes an appropriate heat balance between generation and radiation of heat to restrain its temperature increase.
If it is impossible to employ such a technique as to increase sufficiently the outer surface and heat capacity of the parts, the following conventional methods are used. For instance, there is formed a heat sink to be connected to such an electric device as a power transistor and to radiate heat of the transistor. Another method is to blow air by using a fan onto a targeted device surface to remove forcibly heat therefrom.
An electric rotary machine, like a stepping motor and so on, has cores of soft magnetic material around which coils are wound, and is rotated by magnetic flux passing through the cores which is caused by an electric current flowing in the windings of the coils.
An electric current flowing in a wound coil causes some quantity of heat therein. At the same time it generates magnetic flux to go through the core and also causes some heat therein because of magnetic resistance of the core.
The heat brought by the magnetic flux is radiated from a surface of the core into an atmosphere. This core is conventionally made of a plurality of laminate sheets each of which results resulted from punching an original magnetic sheet.
It is further explained below about parts of a magnetic rotary machine obtained by laminating a plurality of punched magnetic sheets.
The punched magnetic sheets, each of which is shown in FIG. 10, are laminated in congruency with each other to form a laminated body 51 for the parts as illustrated in FIG. 11 (it illustrates an example of a stator core of a stepping motor.). Thus, a stepping motor is obtained as shown in FIG. 12.
In FIG. 12, the numerals of 52, 53 and 54 represent a rotary shaft, a magnet secured to the rotary shaft 52 and a coil wound around the laminated body 51 (a stator core). Heat generated inside the stepping motor 55 is radiated from the surface thereof toward the surrounding atmosphere. However, in case that such radiation is insufficient for cooling, it is necessary to adopt any of the following measures of enlarging dimensions of a stepping motor, connecting a heat source to a heat sink outside, and blowing air onto an outer surface of a stepping motor to forcibly radiate heat toward the surrounding air.
In design of a transformer having a core of magnetic laminate sheets, the core needs to be provided with a minimum essential cross-sectional area through which the necessary magnetic flux must pass depending upon the design requirement. However, as a result of designing a small size transformer according to such a manner, it reaches such a problem that a temperature of the magnetic core is gradually increased because of insufficient heat radiation therefrom.
To avoid the problem, a conventional method is to make a size of a magnetic core larger than that to be required in view of the design method mentioned above.
On the other hand, there is a demand for reducing an outer size of a magnetic core to be as small as possible because recently it is valued to make an electric apparatus small and compact.
In the electric assemblies like electronic parts, electric rotary machines and transformers mentioned above, there appear the following problems. That is, if heat generated in the assembly is handled to be removed by natural radiation, the assembly naturally becomes large in size. Using a heat sink for radiation, requires a lot of metalworking steps including molding a metal body with fins for a heat sink and subjecting the heat sink to a cutting process to form a plain surface thereon for connection with the assembly. Moreover, such a heat sink is expensive because of increases of the number of manufacturing steps and also makes the resultant assembly large in size. If a heat sink is provided with an air blowing means like a cooling fan, the resultant product becomes large and expensive after all.